<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <button id="btn">123123</button>
</body>
<script>
    const buttonDom = document.getElementById('btn')

    buttonDom.addEventListener('click',clickA)

    buttonDom.addEventListener('click',clickB)

    function clickA(){
        console.log('A')
    }
    function clickB(){
        console.log('B')
    }
</script>
</html>